1. Field of the Invention
The present invention relates to a cryogenic refrigerator, a cryopump and a displacer that include a resin provided on a surface of the displacer.
2. Description of the Related Art
Conventionally, a cryogenic refrigerator is known that uses a refrigerant gas such as a helium gas, drives a displacer in a cylinder, and generates cooling by expanding the refrigerant gas in the cylinder. For example, a Gifford-McMahon (which may be called “GM”) refrigerator is used as a cryogenic refrigerator.
This GM cryogenic refrigerator once implemented can generate cooling of about 10 K by being made multistage. Accordingly, the GM cryogenic refrigerator is often used for a cryopump and the like that evacuate a vacuum chamber of a semiconductor fabrication apparatus and the like to make a vacuum.
Furthermore, one of the GM cryogenic refrigerators is configured to include a displacer, an outer circumferential surface of which is coated with a resin to improve a sealing characteristic as disclosed in Japanese Patent No. 3588644. Conventionally, a thickness of the resin is formed uniformly on the whole outer circumferential surface.